In deeper high temperature gas wells now being drilled, certain seals in the wellhead may be subjected to an internal pressure of up to 30,000 p.s.i., and need to be able to remain in place unobserved and unattended and remain reliable over a several year period, where the operating temperature range incumbent on the seals may be -75.degree. F. to 600.degree. F.
Conventionally, in wellheads, metal ring seals have been used in bolted flanges and clamped between ends provided with especially tapered surfaces. However, these conventional sealing rings have been discovered to be not entirely suitable when used in such a high pressure, high temperature environment. Resilient seals have been found to be less than totally reliable due to insufficient resistance to chemical attack and to high operating temperature.
In one widely used conventional type of seal assembly, a metal seal is crushed against tapers, such as the A.P.I. rings. Connectors were designed to provide a predetermined degree of stand-off between two parts in order to provide a desired, adequate amount of crushing of the intervening seal member. In another prior art variation, a ring-type seal was arranged to be exposed to internal pressure in such a way that an increase in pressure increased the seal ring energization pressure to prevent leakage at high pressure.